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1.
Developing novel materials that tolerate thickness variations of the active layer is critical to further enhance the efficiency of polymer solar cells and enable large‐scale manufacturing. Presently, only a few polymers afford high efficiencies at active layer thickness exceeding 200 nm and molecular design guidelines for developing successful materials are lacking. It is thus highly desirable to identify structural factors that determine the performance of semiconducting conjugated polymers in thick‐film polymer solar cells. Here, it is demonstrated that thiophene rings, introduced in the backbone of alternating donor–acceptor type conjugated polymers, enhance the fill factor and overall efficiency for thick (>200 nm) solar cells. For a series of fluorinated semiconducting polymers derived from electron‐rich benzo[1,2‐b:4,5‐b′]dithiophene units and electron‐deficient 5,6‐difluorobenzo[2,1,3]thiazole units a steady increase of the fill factor and power conversion efficiency is found when introducing thiophene rings between the donor and acceptor units. The increased performance is a synergistic result of an enhanced hole mobility and a suppressed bimolecular charge recombination, which is attributed to more favorable polymer chain packing and finer phase separation.  相似文献   
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During the larval stages of development, the imaginal disc of Drosphila Melanogaster is composed by a monolayer of epithelial cells, which undergo a strain actively produced by the cells themselves. The well-organized collective contraction produces a stress field that seemingly has a double morphogenetic role: it orchestrates the cellular organization towards the macroscopic shape emergence while simultaneously providing a local information on the organ size. Here we perform numerical simulations of such a mechanical control on morphogenesis at a continuum level, using a three-dimensional finite model that accounts for the active cell contraction. The numerical model is able to reproduce the (few) known qualitative characteristics of the tensional patterns within the imaginal disc of the fruit fly. The computed stress components slightly deviate from planarity, thus confirming the previous theoretical assumptions of a nonlinear elastic analytical model, and enforcing the hypothesis that the spatial variation of the mechanical stress may act as a size regulating signal that locally scales with the global dimension of the domain.  相似文献   
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华北低丘山地人工林蒸散的控制因子   总被引:1,自引:0,他引:1  
黄辉  孟平  张劲松  郑宁  贾长荣 《生态学报》2014,34(3):667-673
人工林蒸散的影响机制研究对指导我国林业生态工程建设有重要意义。基于涡度相关技术,对华北低丘山区30年生栓皮栎-刺槐-侧柏人工混交林进行了连续2a的观测,以探讨蒸散的控制因子。结果表明:退耦系数(Ω)与冠层导度的季节动态有很好的一致性。2007、2008年的快速生长季Ω变化范围分别为0.12—0.62、0.08—0.54,平均值分别为0.37、0.23,快速生长季蒸散主要受气孔控制。2008年比2007年偏旱,该年快速生长季的退耦系数、冠层导度和蒸散低于2007年,发生干旱时蒸散主要受气孔限制。气孔对蒸散的限制作用在大气湿度较低时较高,并且这种限制作用在发生干旱时会进一步加剧。快速生长季内辐射是影响蒸散的主要环境因子,辐射资源丰富的年份气孔对蒸散的控制程度更高。  相似文献   
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Species boundaries and phylogenetic relationships of 17 taxa ofAnthriscus (Apiaceae), with special emphasis on the critical sect.Cacosciadium, were explored using morphological data with principal component analysis, phenetics, and phylogenetics. The analyses did not provide satisfactory resolution of taxa from sect.Cacosciadium and only four species were retained. The total number of species was reduced to nine. Sect.Cacosciadium is distinguished by only two synapomorphies while sects.Anthriscus andCaroides are better supported. Present geographic and ecological variation suggests that the radiation ofAnthriscus occurred through divergence of peripheral isolated populations adapting to different habitats: high montane meadows and screes, shady climax forests, and seasonally dry habitats at lower altitudes. The adaptive significance of particular morphological traits is discussed.  相似文献   
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The molecular signals that regulate mitotic spindle orientation to determine the proper division axis play a critical role in the development and maintenance of tissue homeostasis. However, deregulation of signaling events can result in spindle misorientation, which in turn can trigger developmental defects and cancer progression. Little is known about the cellular signaling pathway involved in the misorientation of proliferating cells that evade apoptosis after DNA damage. In this study, we found that perturbations to spindle orientation were induced in ultraviolet C (UVC)-irradiated surviving cells. N-terminal truncated Rho GDP-dissociation inhibitor β (RhoGDIβ), which is produced by UVC irradiation, distorted the spindle orientation of HeLa cells cultured on Matrigel. The short hairpin RNA-mediated knockdown of RhoGDIβ significantly attenuated UVC-induced misorientation. Subsequent expression of wild-type RhoGDIβ, but not a noncleavable mutant, RhoGDIβ (D19A), again led to a relative increase in spindle misorientation in response to UVC. Our findings revealed that RhoGDIβ impacts spindle orientation in response to DNA damage.  相似文献   
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To investigate the possible mechanisms for biological effects of 1,800 MHz mobile radiofrequency radiation (RFR), the radiation-specific absorption rate was applied at 2 and 4 W/kg, and the exposure mode was 5 min on and 10 min off (conversation mode). Exposure time was 24 h short-term exposure. Following exposure, to detect cell DNA damage, cell apoptosis, and reactive oxygen species (ROS) generation, the Comet assay test, flow cytometry, DAPI (4′,6-diamidino-2-phenylindole dihydrochloride) staining, and a fluorescent probe were used, respectively. Our experiments revealed that mobile phone RFR did not cause DNA damage in marginal cells, and the rate of cell apoptosis did not increase (P > 0.05). However, the production of ROS in the 4 W/kg exposure group was greater than that in the control group (P < 0.05). In conclusion, these results suggest that mobile phone energy was insufficient to cause cell DNA damage and cell apoptosis following short-term exposure, but the cumulative effect of mobile phone radiation still requires further confirmation. Activation of the ROS system plays a significant role in the biological effects of RFR. Bioelectromagnetics. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals, Inc.  相似文献   
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Based on central dogma of genetics, protein is the embodiment and executor of genetic function, post-translational modifications (PTMs) of protein are particularly important and involved in almost all aspects of cell biology and pathogenesis. Studies have shown that ionizing radiation (IR) alters gene expression much more profoundly and a broad variety of cell-process pathways, lots of proteins are modified and activated. Our understanding of the protein in response to ionizing radiation is steadily increasing. Among the various biological processes known to induce radioresistance, PTMs have attracted marked attention in recent years. The present review summarizes the latest knowledge about how PTMs response to ionizing radiation and pathway analysis were conducted. The data provided insights into biological effects of IR and contributing to the development of novel IR-based strategies.  相似文献   
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IntroductionOur markerless tumor tracking algorithm requires 4DCT data to train models. 4DCT cannot be used for markerless tracking for respiratory-gated treatment due to inaccuracies and a high radiation dose. We developed a deep neural network (DNN) to generate 4DCT from 3DCT data.MethodsWe used 2420 thoracic 4DCT datasets from 436 patients to train a DNN, designed to export 9 deformation vector fields (each field representing one-ninth of the respiratory cycle) from each CT dataset based on a 3D convolutional autoencoder with shortcut connections using deformable image registration. Then 3DCT data at exhale were transformed using the predicted deformation vector fields to obtain simulated 4DCT data. We compared markerless tracking accuracy between original and simulated 4DCT datasets for 20 patients. Our tracking algorithm used a machine learning approach with patient-specific model parameters. For the training stage, a pair of digitally reconstructed radiography images was generated using 4DCT for each patient. For the prediction stage, the tracking algorithm calculated tumor position using incoming fluoroscopic image data.ResultsDiaphragmatic displacement averaged over 40 cases for the original 4DCT were slightly higher (<1.3 mm) than those for the simulated 4DCT. Tracking positional errors (95th percentile of the absolute value of displacement, “simulated 4DCT” minus “original 4DCT”) averaged over the 20 cases were 0.56 mm, 0.65 mm, and 0.96 mm in the X, Y and Z directions, respectively.ConclusionsWe developed a DNN to generate simulated 4DCT data that are useful for markerless tumor tracking when original 4DCT is not available. Using this DNN would accelerate markerless tumor tracking and increase treatment accuracy in thoracoabdominal treatment.  相似文献   
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